On Sun, 5 Apr 2020 12:17:03 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 2020-04-05 11:42, jlarkin@highlandsniptechnology.com wrote: >> On Sun, 5 Apr 2020 10:52:29 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 2020-04-05 00:09, jlarkin@highlandsniptechnology.com wrote: >>>> On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote: >>>> >>>>> Following up on blocher's sterling work,(*) >>>>> >>>>> Many of us use parts off-label, often very successfully. A few >>>>> examples: >>>>> >>>>> SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is >>>>> around 12 GHz, but they're amazingly stable. >>>> >>>> They make excellent switches too. Rds-on is never specified for RF >>>> parts, but it's about 2 ohms for the 551. >>>> >>>>> >>>>> 74HC4352s make good flying-capacitor diff amp front ends. >>>>> >>>>> TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is >>>>> almost in a class with relays, but 1E5 times faster. >>>>> >>>>> Zero-ohm jumpers have about the right resistance to stabilize LDO >>>>> regulators with ceramic output caps. (It's good to be able to >>>>> disconnect the supplies during bring-up, and putting the jumper >>>>> between the reg and the output cap has this additional benefit. >>>>> >>>>> Your faves? >>>> >>>> Some digital bus and USB switches are cheap and are excellent, >>>> super-fast analog multiplexers. >>>> >>>> Some chips are useful just for their ESD diodes. >>>> >>>> LVDS line receivers are super-fast, dirt cheap RRIO comparators. >>> >>> I've used them like that at your suggestion. Snazzy if you don't need >>> super low offset voltage. (And if you do, every comparator slows way down.) >>> >>>> >>>> An LED can be used as the voltage reference for an NPN current >>>> source. The tempcos can be made to almost cancel. >>>> >>>> High value AlN resistors can be used as thermal bridges. >>> >>> That's interesting. I recall discussing some very expensive parts sold >>> specifically for DC isolating thermal pours. >>> >>>> >>>> Surface-mount platinum RTDs can be used in experiments, as both >>>> heater and sensor, to quantify resistor heat sinking and thermal >>>> transients. >>>> >>>> Surface-mount resistors can be last-resort fuses. >>>> >>>> Low-barrier schottky diodes can be used in reverse as >>>> constant-current things. Tempcos are not great. The same diode can >>>> charge and discharge a capacitor. >>> >>> Interesting. Are they reasonably repeatable unit-to-unit? >> >> For modest values of reasonable. It's Is, which is huge for >> schottkies, hundred nA sorts of numbers. I've posted my RF detector >> which is a diode and a capacitor. It's in production. >> >>> >>>> >>>> Some self-protecting SSRs can be used as electronic fuses. As can a >>>> 3t regulator with the adj pin open. >>>> >>>> Depletion fets are nice capacitor bleeders. Ditto 3t reg as a >>>> current sink. >>> >>> >>>> >>>> A bit of open-load transmission line can be a high-frequency peaker. >>>> I have that option in my GHz o/e layout. >>> >>> Interesting. How does that work? Normally I think of O/C tlines as a >>> series resonance to ground. >> >> Stick a drooling-rise step into one end of a transmission line and it >> will overshoot and snap up the waveform at the other end. Adjust the >> source impedance, or terminate a little, to trim the step response. >> It's sharper than RC peaking, so compensates things like Ft rolloff or >> skin effect. > >Okay, so not really open-circuited. I'll try it out. That could >potentially have helped that single-diode sampler gizmo--its speed was >limited by the rise time of the line receiver driving the pHEMT switch. >That one used a capacitor plus a short, mismatched shunt stub to make >the sampling pulse from a falling edge.The soft peaking helps when a step has a soft corner on the rise, which is very common. That's why people who do fast stuff cheat and measure risetime 20/80.> >> >> I had a profound, life-changing revelation recently. If you don't poke >> a fast rise into a passive transmission line, you won't get a fast >> reflection. I wasted all those years designing absorptive lowpass >> filters. > >Gasp! ;) > >> >>> >>> >>>> >>>> Someone said never use an opamp as a comparator. They were wrong. >>> >>> Gotta watch for the antiparallel diodes on the inputs, though. For slow >>> stuff, LM358s work great as comparators--the inputs survive going way >>> above the supply. >>> >>>> >>>> An rro opamp can also be used as a current limiter/fuse. >>>> >>>> You can do all sorts of things with ribbon cable. >>>> >>>> Some HV diodes and the c-b junctions of some transistors make >>>> awesome drift step-recovery (Grehkov) diodes. >>>> >>>> BFT25s can be used as fA-leakage diodes. >>>> >>>> Dual-winding inductors, like DRQ127, can do all kinds of tricks. >>> >>> Annoying that they don't tell you k in the datasheet, and you can't even >>> back it out from the series-connected inductance, which is quoted as >>> exactly four times the parallel-connected value. >> >> The k's are really high. Easy to measure. > >That's unusual for a 'coupled inductor'. I normally expect it to be >around 0.85.The DRQs are bifilar. Two or three 9's. And a lot of capacitance. They make nice autotransformer flybacks. Does that have a better name?>>>> A toroidal inductor can be a liquid level sensor. >>> >>> That one I haven't heard about. Are you looking for the NMR signal? ;) >> >> A conductive liquid is a shorted turn. > >At sufficiently low frequency, anyway. > >We've started putting little Sensirion T/H sensors in a lot of things. >When using TECs, it's awfully nice to be able to compute the dew point, >for instance, and in outdoor applications (e.g. our fire sensors for >harvesters) it's good to be able to predict when the window is liable to >fog up on the inside. > >We use IP67+ enclosures with bags of 5A molecular sieve inside, which is >super cheap and will absorb 50% of its own mass in water. Simon has had >to learn a whole lot about enclosures and mechanical design generally. >Turns out that you have to put an air vent on the enclosure to prevent >pumping water inside due to atmospheric pressure differences. That >leads to working of the O-ring seals, which wears them out. > >We considered using a bellows, but atmospheric pressure varies +-7% or >so, which makes for a pretty big, floppy bellows. Hermetic construction >is possible but very expensive, and relies on glass or ceramic insulated >connectors. The glass would have had to be brazed or indium-soldered to >the lid, which leads to CTE mismatch problems.A balloon inside? -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Favourite parts with off-label uses?
Started by ●April 4, 2020
Reply by ●April 5, 20202020-04-05
Reply by ●April 5, 20202020-04-05
On Saturday, April 4, 2020 at 8:49:22 PM UTC-4, pcdh...@gmail.com wrote:> Following up on blocher's sterling work,(*) > > Many of us use parts off-label, often very successfully. A few examples: > > SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable. > > 74HC4352s make good flying-capacitor diff amp front ends. > > TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster. > > Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit. > > Your faves?Wow nice list! I'd like to take a 'part' off the alt. use list. I use to tout the use of 20 zeners rev biased at ~10-100 uA as audio noise sources. When I went to replace the pack I had it turned out I had a 'golden string'. I had to order a bunch from different suppliers to find noisy batch. (And that still wasn't as good(noisy) as the original... but it's obvious that almost no one wants a noisy zener.) George H.> > Cheers > > Phil Hobbs > (*) who may be bulegoge's good twin, given the similarity of their emails ;) > > -- > Dr Philip C D Hobbs > Principal Consultant > ElectroOptical Innovations LLC / Hobbs ElectroOptics > Optics, Electro-optics, Photonics, Analog Electronics > Briarcliff Manor NY 10510 > > http://electrooptical.net > http://hobbs-eo.com
Reply by ●April 5, 20202020-04-05
On Sunday, April 5, 2020 at 8:42:58 AM UTC-7, jla...@highlandsniptechnology.com wrote:> On Sun, 5 Apr 2020 10:52:29 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: >>On 2020-04-05 00:09, jla...@highlandsniptechnology.com wrote:> >> Why are there no surface-mount fans? > > > >Dunno, but maybe because high temperature engineering plastic is > >expensive. You could probably make them with graphite block bearings. > > We're putting fans on PCBs with angle brackets. A fan blowing directly > on parts is wonderful thermally. Almost like they designed them to do > that.Historically, if the parts might be muffins, they did. The surface-flow fans on high-end video cards are axial-in/circumference-out air movers, a variant on the bottom-sucking sump pump designs of indeterminate age. Ducting (housing) gets in the way of IR for surface-mount parts, even if you can afford the materials. So, you'd want to surface-mount a connector at the western edge of the footprint, and rout an aperture (or apertures) at the eastern edge, then after reflow, the fan hooks onto the aperture and swings down to mate with the connector. Wire-tie or latching connector keep it in place. Or glue... but moving parts are best kept replaceable.
Reply by ●April 5, 20202020-04-05
On Sunday, April 5, 2020 at 12:09:59 AM UTC-4, jla...@highlandsniptechnology.com wrote:> On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote: > > >Following up on blocher's sterling work,(*) > > > >Many of us use parts off-label, often very successfully. A few examples: > > > >SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is around 12 GHz, but they're amazingly stable. > > They make excellent switches too. Rds-on is never specified for RF > parts, but it's about 2 ohms for the 551. > > > > >74HC4352s make good flying-capacitor diff amp front ends. > > > >TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is almost in a class with relays, but 1E5 times faster. > > > >Zero-ohm jumpers have about the right resistance to stabilize LDO regulators with ceramic output caps. (It's good to be able to disconnect the supplies during bring-up, and putting the jumper between the reg and the output cap has this additional benefit. > > > >Your faves? > > Some digital bus and USB switches are cheap and are excellent, > super-fast analog multiplexers. > > Some chips are useful just for their ESD diodes. > > LVDS line receivers are super-fast, dirt cheap RRIO comparators. > > An LED can be used as the voltage reference for an NPN current source. > The tempcos can be made to almost cancel. > > High value AlN resistors can be used as thermal bridges. > > Surface-mount platinum RTDs can be used in experiments, as both heater > and sensor, to quantify resistor heat sinking and thermal transients. > > Surface-mount resistors can be last-resort fuses. > > Low-barrier schottky diodes can be used in reverse as constant-current > things. Tempcos are not great. The same diode can charge and discharge > a capacitor. > > Some self-protecting SSRs can be used as electronic fuses. As can a 3t > regulator with the adj pin open. > > Depletion fets are nice capacitor bleeders. Ditto 3t reg as a current > sink. > > A bit of open-load transmission line can be a high-frequency peaker. I > have that option in my GHz o/e layout. > > Someone said never use an opamp as a comparator. They were wrong. > > An rro opamp can also be used as a current limiter/fuse. > > You can do all sorts of things with ribbon cable. > > Some HV diodes and the c-b junctions of some transistors make awesome > drift step-recovery (Grehkov) diodes. > > BFT25s can be used as fA-leakage diodes. > > Dual-winding inductors, like DRQ127, can do all kinds of tricks. > > Microwave MMICS can be fabulous pulse amplifiers. > > Zeners are good noise generators. > > 3t regulators can be good power amplifiers > > Phemts can make amazing diodes. Too bad they are mostly gone. > > Inside an FPGA, a dual-port sram can make an otherwise impossible > giant crossbar switch. > > LVDS inputs on an FPGA make OK comparators. > > Violating setup/hold specs on fast flipflops can be interesting. > > Gates are delay lines. > > One dual optocoupler can make a great high voltage amplifier output > stage. No level shifting problems. > > PV optocouplers can be used as floating power supplies. > > Unshielded drum-core inductors can be mag field sensors or > high-voltage signal/power isolators. > > A toroidal inductor can be a liquid level sensor. > > Trimpots can be decoded as 2, 3, maybe even 4 position switches. Or > use a high resistance pot as an SPDT on-off-on switch. > > Why are there no surface-mount fans?Oh nice. Reverse biased (red GaAs) led's as single photon detectors. George H.> > > > > > -- > > John Larkin Highland Technology, Inc > > Science teaches us to doubt. > > Claude Bernard
Reply by ●April 5, 20202020-04-05
Reply by ●April 5, 20202020-04-05
On Sunday, April 5, 2020 at 11:42:58 AM UTC-4, jla...@highlandsniptechnology.com wrote:> On Sun, 5 Apr 2020 10:52:29 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > > >On 2020-04-05 00:09, jlarkin@highlandsniptechnology.com wrote: > >> On Sat, 4 Apr 2020 17:49:18 -0700 (PDT), pcdhobbs@gmail.com wrote: > >> > >>> Following up on blocher's sterling work,(*) > >>> > >>> Many of us use parts off-label, often very successfully. A few > >>> examples: > >>> > >>> SAV-551+ pHEMTs make very good wideband bootstraps. Their f_max is > >>> around 12 GHz, but they're amazingly stable. > >> > >> They make excellent switches too. Rds-on is never specified for RF > >> parts, but it's about 2 ohms for the 551. > >> > >>> > >>> 74HC4352s make good flying-capacitor diff amp front ends. > >>> > >>> TMUX1511s make very nice analogue lock-ins--their Coff*Ron FOM is > >>> almost in a class with relays, but 1E5 times faster. > >>> > >>> Zero-ohm jumpers have about the right resistance to stabilize LDO > >>> regulators with ceramic output caps. (It's good to be able to > >>> disconnect the supplies during bring-up, and putting the jumper > >>> between the reg and the output cap has this additional benefit. > >>> > >>> Your faves? > >> > >> Some digital bus and USB switches are cheap and are excellent, > >> super-fast analog multiplexers. > >> > >> Some chips are useful just for their ESD diodes. > >> > >> LVDS line receivers are super-fast, dirt cheap RRIO comparators. > > > >I've used them like that at your suggestion. Snazzy if you don't need > >super low offset voltage. (And if you do, every comparator slows way down.) > > > >> > >> An LED can be used as the voltage reference for an NPN current > >> source. The tempcos can be made to almost cancel. > >> > >> High value AlN resistors can be used as thermal bridges. > > > >That's interesting. I recall discussing some very expensive parts sold > >specifically for DC isolating thermal pours. > > > >> > >> Surface-mount platinum RTDs can be used in experiments, as both > >> heater and sensor, to quantify resistor heat sinking and thermal > >> transients. > >> > >> Surface-mount resistors can be last-resort fuses. > >> > >> Low-barrier schottky diodes can be used in reverse as > >> constant-current things. Tempcos are not great. The same diode can > >> charge and discharge a capacitor. > > > >Interesting. Are they reasonably repeatable unit-to-unit? > > For modest values of reasonable. It's Is, which is huge for > schottkies, hundred nA sorts of numbers. I've posted my RF detector > which is a diode and a capacitor. It's in production. > > > > >> > >> Some self-protecting SSRs can be used as electronic fuses. As can a > >> 3t regulator with the adj pin open. > >> > >> Depletion fets are nice capacitor bleeders. Ditto 3t reg as a > >> current sink. > > > > > >> > >> A bit of open-load transmission line can be a high-frequency peaker. > >> I have that option in my GHz o/e layout. > > > >Interesting. How does that work? Normally I think of O/C tlines as a > >series resonance to ground. > > Stick a drooling-rise step into one end of a transmission line and it > will overshoot and snap up the waveform at the other end. Adjust the > source impedance, or terminate a little, to trim the step response. > It's sharper than RC peaking, so compensates things like Ft rolloff or > skin effect. > > I had a profound, life-changing revelation recently. If you don't poke > a fast rise into a passive transmission line, you won't get a fast > reflection. I wasted all those years designing absorptive lowpass > filters. > > > > > > >> > >> Someone said never use an opamp as a comparator. They were wrong. > > > >Gotta watch for the antiparallel diodes on the inputs, though. For slow > >stuff, LM358s work great as comparators--the inputs survive going way > >above the supply. > > > >> > >> An rro opamp can also be used as a current limiter/fuse. > >> > >> You can do all sorts of things with ribbon cable. > >> > >> Some HV diodes and the c-b junctions of some transistors make > >> awesome drift step-recovery (Grehkov) diodes. > >> > >> BFT25s can be used as fA-leakage diodes. > >> > >> Dual-winding inductors, like DRQ127, can do all kinds of tricks. > > > >Annoying that they don't tell you k in the datasheet, and you can't even > >back it out from the series-connected inductance, which is quoted as > >exactly four times the parallel-connected value. > > The k's are really high. Easy to measure. > > >> > >> Microwave MMICS can be fabulous pulse amplifiers. > >> > >> Zeners are good noise generators. > >> > >> 3t regulators can be good power amplifiers > >> > >> Phemts can make amazing diodes. Too bad they are mostly gone. > > > >Well, MCL is pretty good about keeping stuff in production. > > Yes, but they are little ones. The Avago SOT89s were great 1 amp, 1 > pF, zero recovery diodes. > > > > >> > >> Inside an FPGA, a dual-port sram can make an otherwise impossible > >> giant crossbar switch. > >> > >> LVDS inputs on an FPGA make OK comparators. > >> > >> Violating setup/hold specs on fast flipflops can be interesting. > > > >How so? > > We are measuring timings and jitter to fs resolution by sweeping one > edge across another, clock and D on a GigaComm flipflop, and averaging > the Q output. I have some data if anyone's interested. > > > > >> > >> Gates are delay lines. > > > >Poorly specified ones, though--at least in 74HC, typical propagation > >delay specs are half of the maximum. Of course, my usual rule for > >one-shots is to avoid them unless the circuit would be okay over a 3:1 > >range of delays. > > > That's often all you need, some sort of glitch. > > > > >> > >> One dual optocoupler can make a great high voltage amplifier output > >> stage. No level shifting problems. > >> > >> PV optocouplers can be used as floating power supplies. > >> > >> Unshielded drum-core inductors can be mag field sensors or > >> high-voltage signal/power isolators. > >> > >> A toroidal inductor can be a liquid level sensor. > > > >That one I haven't heard about. Are you looking for the NMR signal? ;) > > A conductive liquid is a shorted turn. >Huh, that's fun. you could play with the frequency. I had an axial inductor, (audio) Q went to hell after a water bath flux wash. I got better when dry, but took a while. (once found inductor was no longer immersed in water.) George H.> > > >> > >> Trimpots can be decoded as 2, 3, maybe even 4 position switches. Or > >> use a high resistance pot as an SPDT on-off-on switch. > > > >BTW, did you find a good replacement for that discontinued Murata PV2A > >one that works up to 1-2 GHz? > > Don't think so. I'll check. Production hates them... hard to adjust. > > > > >> > >> Why are there no surface-mount fans? > > > >Dunno, but maybe because high temperature engineering plastic is > >expensive. You could probably make them with graphite block bearings. > > We're putting fans on PCBs with angle brackets. A fan blowing directly > on parts is wonderful thermally. Almost like they designed them to do > that. > > They could also put tapped holes at 90 degrees. > > > > >Cheers > > > >Phil Hobbs > > > -- > > John Larkin Highland Technology, Inc > > Science teaches us to doubt. > > Claude Bernard
Reply by ●April 5, 20202020-04-05
On Sunday, April 5, 2020 at 3:43:32 PM UTC-4, plastco...@gmail.com wrote:> NXP 74aup2g07 - analog switch > https://assets.nexperia.com/documents/data-sheet/74AUP2G07.pdfHow exactly does that work? -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
Reply by ●April 5, 20202020-04-05
On Sun, 5 Apr 2020 12:43:27 -0700 (PDT), plastcontrol.ru@gmail.com wrote:>NXP 74aup2g07 - analog switch >https://assets.nexperia.com/documents/data-sheet/74AUP2G07.pdfThose are great. I use them to discharge the cap in precision linear-ramp timing circuits. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●April 5, 20202020-04-05
On Sunday, April 5, 2020 at 5:12:12 PM UTC-7, jla...@highlandsniptechnology.com wrote:> On Sun, 5 Apr 2020 12:43:27 -0700 (PDT), plastcontrol.ru@gmail.com > wrote: > > >NXP 74aup2g07 - analog switch > >https://assets.nexperia.com/documents/data-sheet/74AUP2G07.pdf > > Those are great. I use them to discharge the cap in precision > linear-ramp timing circuits.The traditional way to discharge the cap would be a controlled current source, and you take the zero-crossing time to indicate the state of charge instead of using a fast ADC. That way, all cycles discharge the capacitor to the exact same level.
Reply by ●April 5, 20202020-04-05
On 6/4/20 10:12 am, jlarkin@highlandsniptechnology.com wrote:> On Sun, 5 Apr 2020 12:43:27 -0700 (PDT), plastcontrol.ru@gmail.com > wrote: > >> NXP 74aup2g07 - analog switch >> https://assets.nexperia.com/documents/data-sheet/74AUP2G07.pdf > > Those are great. I use them to discharge the cap in precision > linear-ramp timing circuits.I know you're concerned about the C-V curve with your fast ramps. How does this device stack up (against your fave pHEMTs for example)> Clifford Heath
